Mouth radical at the bottom anchors the literal sense — to hold something in the mouth, like a candy or a tear. The image extends naturally to figurative containing: 含义 implication, 含泪 with tears, 含蓄 reserved. What is 'now in the mouth' is contained by it.
Top is 今 'now', here serving as phonetic — jīn drifting to hán via the j/h alternation common in this series (含涵函). The same phonetic grouping appears in 念 'to think of' and 贪 'to crave'; the family hangs together by a held-in, contained feeling.
